3D Bioprinting in Microgravity: Opportunities, Challenges, and Possible Applications in Space.

3D bioprinting has developed tremendously in the last couple of years and enables the fabrication of simple, as well as complex, tissue models. The international space agencies have recognized the unique opportunities of these technologies for manufacturing cell and tissue models for basic research in space, in particular for investigating the effects of microgravity and cosmic radiation on different types of human tissues. In addition, bioprinting is capable of producing clinically applicable tissue grafts, and its implementation in space therefore can support the autonomous medical treatment options for astronauts in future long term and far-distant space missions. The article discusses opportunities but also challenges of operating different types of bioprinters under space conditions, mainly in microgravity. While some process steps, most of which involving the handling of liquids, are challenging under microgravity, this environment can help overcome problems such as cell sedimentation in low viscous bioinks. Hopefully, this publication will motivate more researchers to engage in the topic, with publicly available bioprinting opportunities becoming available at the International Space Station (ISS) in the imminent future.

Bioinks for Space Missions: The Influence of Long-Term Storage of Alginate-Methylcellulose-Based Bioinks on Printability as well as Cell Viability and Function.

Bioprinting is considered a key technology for future space missions and is currently being established on the International Space Station (ISS). With the aim to perform bioink production as a critical and resource-consuming preparatory step already on Earth and transport a bioink cartridge "ready to use" to the ISS, the storability of bioinks is investigated. Hydrogel blends based on alginate and methylcellulose are laden with either green microalgae of the species Chlorella vulgaris or with different human cell lines including immortilized human mesenchymal stem cells, SaOS-2 and HepG2, as well as with primary human dental pulp stem cells. The bioinks are filled into printing cartridges and stored at 4°C for up to four weeks. Printability of the bioinks is maintained after storage. Viability and function of the cells embedded in constructs bioprinted from the stored bioinks are investigated during subsequent cultivation: The microalgae survive the storage period very well and show no loss of growth and functionality, however a significant decrease is visible for human cells, varying between the different cell types. The study demonstrates that storage of bioinks is in principle possible and is a promising starting point for future research, making complex printing processes more effective and reproducible.

Selection of a suitable photosynthetically active microalgae strain for the co-cultivation with mammalian cells.

Preventing hypoxic zones in 3D bioprinted mammalian cell-laden constructs using an internal oxygen supply could enable a more successful cultivation both in vitro and in vivo. In this study, the suitability of green microalgae as photosynthetic oxygen generators within bioprinted constructs was evaluated by defining and investigating important parameters for a successful co-culture. First, we assessed the impact of light-necessary for photosynthesis-on two non-light adapted mammalian cell types and defined red-light illumination and a temperature of 37°C as essential factors in a co-culture. The four thermotolerant microalgae strains Chlorella sorokiniana, Coelastrella oocystiformis, Coelastrella striolata, and Scenedesmus sp. were cultured both in suspension culture and 3D bioprinted constructs to assess viability and photosynthetic activity under these defined co-culture conditions. Scenedesmus sp. proved to be performing best under red light and 37°C as well as immobilized in a bioprinted hydrogel based on alginate. Moreover, the presence of the antibiotic ampicillin and the organic carbon-source glucose, both required for mammalian cell cultures, had no impact on bioprinted Scenedesmus sp. cultures regarding growth, viability, and photosynthetic activity. This study is the first to investigate the influence of mammalian cell requirements on the metabolism and photosynthetic ability of different microalgal strains. In a co-culture, the strain Scenedesmus sp. could provide a stable oxygenation that ensures the functionality of the mammalian cells.

Think outside the box: 3D bioprinting concepts for biotechnological applications - recent developments and future perspectives.

3D bioprinting - the fabrication of geometrically complex 3D structures from biocompatible materials containing living cells using additive manufacturing technologies - is a rapidly developing research field with a broad range of potential applications in fundamental research, regenerative medicine and industry. Currently, research into 3D bioprinting is mostly focused on new therapeutic concepts for the treatment of injured or degenerative tissue by fabrication of functional tissue equivalents or disease models, utilizing mammalian cells. However, 3D bioprinting also has an enormous potential in biotechnology. Due to the defined spatial arrangement of biologically active (non-mammalian) cells in a biomaterial matrix, reaction compartments can be designed according to specific needs, or co-cultures of different cell types can be realized in a highly organized manner to exploit cell-cell interactions. Thus, 3D bioprinting technology can enable new biotechnological concepts, for example, by implementing perfusion systems while protecting shear sensitive cells or performing cascaded bioreactions. Here, we review the use of 3D bioprinting to manufacture defined 3D microenvironments for biotechnological applications using bacteria, fungi, microalgae, plant cells and co-cultures of different cell types. We discuss recent approaches to apply 3D bioprinting in biotechnological applications and - as it is a particular challenge - concepts for the real-time monitoring of the physiological state, growth and metabolic activity of the embedded cells in 3D bioprinted constructs. With these insights, we outline new applications of 3D bioprinting in biotechnology, engineered living materials and space research.

Excited-state structure of copper phenanthroline-based photosensitizers.

Cu diimine complexes present a noble metal free alternative to classical Ru, Re, Ir and Pt based photosensitizers in solution photochemistry, photoelectrochemical or dye-sensitized solar cells. Optimization of these dyes requires understanding of factors governing the key photochemical properties: excited state lifetime and emission quantum yield. The involvement of exciplex formation in the deactivation of the photoexcited state is a key question. We investigate the excited-state structure of [Cu(dmp)2]+ and [Cu(dsbtmp)2]+ (dmp = 2,9-dimethyl-1,10-phenanthroline, dsbtmp = 2,9-di-sec-butyl-3,4,7,8-tetramethyl-1,10-phenanthroline) using pump-probe X-ray absorption spectroscopy (XAS) and DFT. Features of XAS that distinguish flattened tetrahedral site and 5-coordinated geometry with an additional solvent near Cu(II) center are identified. Pump-probe XAS demonstrates that for both complexes the excited state is 4-coordinated. For [Cu(dmp)2]+ the exciplex is 0.24 eV higher in energy than the flattened triplet state, therefore it can be involved in deactivation pathways as a non-observable state that forms slower than it decays. For [Cu(dsbtmp)2]+ the excited-state structure is characterized by Cu-N distances of 1.98 and 2.07 Å and minor distortions, leading to a 3 orders of magnitude longer excited-state lifetime.

Structure-Activity and Stability Relationships for Cobalt Polypyridyl-Based Hydrogen-Evolving Catalysts in Water.

A series of eight new and three known cobalt polypyridyl-based hydrogen-evolving catalysts (HECs) with distinct electronic and structural differences are benchmarked in photocatalytic runs in water. Methylene-bridged bis-bipyridyl is the preferred scaffold, both in terms of stability and rate. For a cobalt complex of the tetradentate methanol-bridged bispyridyl-bipyridyl complex [CoII Br(tpy)]Br, a detailed mechanistic picture is obtained by combining electrochemistry, spectroscopy, and photocatalysis. In the acidic branch, a proton-coupled electron transfer, assigned to formation of CoIII -H, is found upon reduction of CoII , in line with a pKa (CoIII -H) of approximately 7.25. Subsequent reduction (-0.94 V vs. NHE) and protonation close the catalytic cycle. Methoxy substitution on the bipyridyl scaffold results in the expected cathodic shift of the reduction, but fails to change the pKa (CoIII -H). An analysis of the outcome of the benchmarking in view of this postulated mechanism is given along with an outlook for design criteria for new generations of catalysts.

Sn(IV) Metalloporphyrin/Co(III) Complex: An All-Abundant-Element System for the Photocatalytic Production of H2 in Aqueous Solution.

A new, molecular system for the light-driven production of hydrogen in aqueous solution was developed by combining a water-soluble tin porphyrin ([Sn(IV)Cl2TPPC], A) acting as photosensitizer with a cobalt-based proton-reduction catalyst ([Co(III)Cl(dmgH)2(py)], C). Under visible light illumination and with triethanolamine (TEOA) as electron source, the system evolves H2 for hours and is clearly catalytic in both dye and catalyst. A detailed analysis of the relevant redox potentials in combination with time-resolved spectroscopy resulted in the development of a Z-scheme type model for the flow of electrons in this system. Key intermediates of the proposed mechanism for the pathway leading to H2 are the porphyrin dye's highly oxidizing singlet excited state (1)A* (E ∼ +1.3 V vs NHE), its strongly reducing isobacteriochlorin analogue (E ∼ +0.95 V), and the Co(I) form of C (E ∼ -0.8 V), acting as catalyst for H2 formation. Among other results, the suggested reaction sequence is supported by the detection of a shortened excited-state lifetime for singlet (1)A* (τ ∼ 1.75 ns) in the presence of TEOA and the ultraviolet-visible detection of the Sn(IV) isobacteriochlorin intermediate at λ = 610 nm. Thus, a molecular, conceptually biomimetic, and precious-metal-free reaction chain was found which photocatalytically generates H2 in a 100% aqueous system from an electron donor with a high oxidation potential (E(TEOA) ∼ +1.1 V). On the other hand, at identical conditions, this photoreaction chain yields H2 markedly slower than a system using the photosensitizer [Re(I)(CO)3(bpy) (py)](+), probably due to the much longer excited-state lifetime (τ ∼ 120 ns) of the rhenium dye and better electron-transfer rates caused by its simple single-electron photoreduction chemistry.

Effect of tension-free vaginal tape operation on urethral closure function.

OBJECTIVES: To evaluate whether the tension-free vaginal tape operation changes urethral hypermobility, funneling, and urethral urodynamic parameters in different parts of the urethra. METHODS: We conducted a cohort study of our first 80 unselected female patients (age 36 to 78 years, median 53) undergoing a tension-free vaginal tape procedure. Urethral pressure profile measurements were done before and 6 and 12 months after the operation. Lateral cystography was performed before and after surgery in 50 patients. Of the 80 women, 29 had previously undergone prolapse or incontinence surgery. Parameter-free techniques were used for statistical evaluation. RESULTS: Five patients were lost to follow-up. On an intention-to-treat basis, 66% of the patients were objectively and subjectively cured, 20% were objectively dry but subjectively occasionally incontinent, and 14% had treatment failure. The maximal urethral closure pressure at rest showed no significant changes (median baseline and 6 and 12 months postoperatively, 44, 40, and 38 cm H(2)O, respectively). The pressure transmission ratio increased in the proximal urethra (median 107.5%, 122.5%, and 123.5% at baseline and 6 and 12 months postoperatively, respectively, P <0.05) and distal urethra (median 80%, 112%, 107.5% at baseline and 6 and 12 months postoperatively, respectively, P <0.01). The downward movement of the bladder neck during the Valsalva maneuver decreased (median 2.3 cm preoperatively versus 1.7 cm postoperatively, P <0.001). Urethral rotation was diminished (median 35.5 degrees versus 23 degrees , P <0.01). Funneling was seen postoperatively in only 5 of 25 preoperative cases. CONCLUSIONS: The tension-free vaginal tape procedure stabilizes the urethra anatomically and improves funneling and pressure transmission ratios all along the urethra. The maximal urethral closure pressure at rest decreased without statistical significance.

Polycystic ovaries, obesity and insulin resistance in women with epilepsy. A comparative study of carbamazepine and valproic acid in 105 women.

In order to investigate the possible role of valproic acid therapy in the development of obesity, hyperinsulinism and polycystic ovaries (PCOs), we have studied metabolic parameters and ovarian morphology in epileptic women. A total of 105 women, who were treated for at least 2 years with valproate (n = 52) or carbamazepine monotherapy (n = 53), were included in the examination. Menstrual disturbances were reported by 29 (28 %) of the women, 12 (11 %) of the VPA treated women, and 17 (16 %) in the CBZ group. On ultrasound scan polycystic ovaries were found in 28 patients (27 %) of the whole study population, of whom 13 (12 %) received VPA and 15 (14 %) CBZ. The mean body mass index (BMI) was significantly higher in the VPA group (24.4 kg/m(2) +/- 4.1) than in CBZ treated patients (22.9 kg/m(2) +/- 2.4;p < 0.022), and serum triglycerides tended to be increased, while total cholesterol values (178.9 +/- 30.5) and LDL-cholesterol values (92.6 +/- 27.4) were significantly lower in the valproate group, than in the carbamazepine group (207.1 +/- 43.0 vs 115.1 +/- 42.0; p < 0.001). Postprandial insulin, C-peptide and proinsulin levels were significantly higher in VPA treated patients compared with those treated with CBZ, while no differences could be found in the fasting state. In conclusion we could thus demonstrate that the frequency of PCOs in 27 % of epileptic women seems to be similar to that in the general population with a frequency of 20-30 %. The development of PCOs did not reveal a difference with the administration of VPA or CBZ. With respect to the metabolic side-effects of VPA therapy our data indicate that VPA increases glucose stimulated pancreatic insulin secretion, which might be followed by an increase in body weight.